<?php
/**
* 常用对称加密算法类
* 支持密钥：64/128/256 bit（字节长度8/16/32）
* 支持算法：DES/AES（根据密钥长度自动匹配使用：DES:64bit AES:128/256bit）
* 支持模式：CBC/ECB/OFB/CFB
* 密文编码：base64字符串/十六进制字符串/二进制字符串流
* 填充方式: PKCS5Padding（DES）
*

include "cls.xcrypt.php";

echo '<pre>';
//////////////////////////////////////
$a = isset($_GET['a']) ? $_GET['a'] : '测试123';

//密钥
$key = '12345678123456781234567812345678'; //256 bit
$key = '1234567812345678'; //128 bit
$key = '12345678'; //64 bit

//设置模式和IV
$m = new Xcrypt($key, 'cbc', 'auto');

//获取向量值
echo '向量：';
var_dump($m->getIV());

//加密
$b = $m->encrypt($a, 'base64');
//解密
$c = $m->decrypt($b, 'base64');
/////////////////////////////////////////
echo '</pre>';
*/

class Xcrypt {

  private $mcrypt;
  private $key;
  private $mode;
  private $iv;
  private $blocksize;

  /**
   * 构造函数
   *
   * @param string 密钥
   * @param string 模式
   * @param string 向量（"off":不使用 / "auto":自动 / 其他:指定值，长度同密钥）
   */
  public function __construct($key, $mode = 'cbc', $iv = "off") {
    switch (strlen($key)){
    case 8:
      $this->mcrypt = MCRYPT_DES;
      break;
    case 16:
      $this->mcrypt = MCRYPT_RIJNDAEL_128;
      break;
    case 32:
      $this->mcrypt = MCRYPT_RIJNDAEL_256;
      break;
    default:
      die("Key size must be 8/16/32");
    }

    $this->key = $key;

    switch (strtolower($mode)){
    case 'ofb':
      $this->mode = MCRYPT_MODE_OFB;
      if ($iv == 'off') {
        die('OFB must give a IV'); //OFB必须有向量
      }
      break;
    case 'cfb':
      $this->mode = MCRYPT_MODE_CFB;
      if ($iv == 'off') {
        die('CFB must give a IV'); //CFB必须有向量
      }
      break;
    case 'ecb':
      $this->mode = MCRYPT_MODE_ECB;
      $iv = 'off'; //ECB不需要向量
      break;
    case 'cbc':
    default:
      $this->mode = MCRYPT_MODE_CBC;
    }

    switch (strtolower($iv)){
    case "off":
      $this->iv = null;
      break;
    case "auto":
      $source = PHP_OS=='WINNT' ? MCRYPT_RAND : MCRYPT_DEV_RANDOM;
      $this->iv = mcrypt_create_iv(mcrypt_get_block_size($this->mcrypt, $this->mode), $source);
      break;
    default:
      $this->iv = $iv;
    }


  }


  /**
   * 获取向量值
   * @param string 向量值编码（base64/hex/bin）
   * @return string 向量值
   */
  public function getIV($code = 'base64') {
    switch ($code){
    case 'base64':
      $ret = base64_encode($this->iv);
      break;
    case 'hex':
      $ret = bin2hex($this->iv);
      break;
    case 'bin':
    default:
      $ret = $this->iv;
    }
    return $ret;
  }


  /**
   * 加密
   * @param string 明文
   * @param string 密文编码（base64/hex/bin）
   * @return string 密文
   */
  public function encrypt($str, $code = 'base64') {
    if ($this->mcrypt == MCRYPT_DES) {
      $str = $this->_pkcs5Pad($str);
    }

    if (isset($this->iv)) {
      $result = mcrypt_encrypt($this->mcrypt, $this->key, $str, $this->mode, $this->iv);
    } else {
      @$result = mcrypt_encrypt($this->mcrypt, $this->key, $str, $this->mode);
    }

    switch ($code){
    case 'base64':
      $ret = base64_encode($result);
      break;
    case 'hex':
      $ret = bin2hex($result);
      break;
    case 'bin':
    default:
      $ret = $result;
    }

    return $ret;

  }

  /**
   * 解密
   * @param string 密文
   * @param string 密文编码（base64/hex/bin）
   * @return string 明文
   */
  public function decrypt($str, $code = "base64") {
    $ret = false;

    switch ($code){
    case 'base64':
      $str = base64_decode($str);
      break;
    case 'hex':
      $str = $this->_hex2bin($str);
      break;
    case 'bin':
    default:
    }

    if ($str !== false) {
      if (isset($this->iv)) {
        $ret = mcrypt_decrypt($this->mcrypt, $this->key, $str, $this->mode, $this->iv);
      } else {
        @$ret = mcrypt_decrypt($this->mcrypt, $this->key, $str, $this->mode);
      }
      if ($this->mcrypt == MCRYPT_DES) {
        $ret = $this->_pkcs5Unpad($ret);
      }
      $ret = trim($ret);
    }

    return $ret;
  }



  private function _pkcs5Pad($text) {
    $this->blocksize = mcrypt_get_block_size($this->mcrypt, $this->mode);
    $pad = $this->blocksize - (strlen($text) % $this->blocksize);
    return $text . str_repeat(chr($pad), $pad);
  }

  private function _pkcs5Unpad($text) {
    $pad = ord($text{strlen($text) - 1});
    if ($pad > strlen($text)) {
      return false;
    }
    if (strspn($text, chr($pad), strlen($text) - $pad) != $pad) {
      return false;
    }
    $ret = substr($text, 0, -1 * $pad);
    return $ret;
  }

  private function _hex2bin($hex = false) {
    $ret = $hex !== false && preg_match('/^[0-9a-fA-F]+$/i', $hex) ? pack("H*", $hex) : false;
    return $ret;
  }

}
